"For years, we didn't have any grandchildren and my daughter's dog, Mr. Moose, was all we had," said 63-year-old Eileen Williams of the San Francisco Bay area.

"You take what you get in life and make the most of it, and we've been pleased he has been a huge part of our family over the years, as our grandpuppy."

Another grandpuppy-parent, 52-year-old Rhonda Shew of Nanaimo, British Columbia, says she has been patiently waiting for grandkids but is satisfied with her two grandpuppies for now.

"I spoil them with dog treats, breath mints and clothes," she said. "We even gave them their own Facebook pages," she said with a chuckle.

Social networking for our pets? Why do we humans like to impose human characteristics on animals?

Eileen and Rick Williams say they adore their grandpuppy, Mr. Moose.

"The ability to put yourself in another person's shoes is important in a species as social as ours," said psychology professor Harold Herzog of Western Carolina University.

"What seems to happen is that we use this tendency to project human mental states into other creatures. It is particularly easy to do this in our pets because we have come to think of them as family members," says the professor.

Evolutionary biologists say the relationship between humans and dogs dates back at least 14,000 years ago -- and dogs have lived in close association with humans longer than any other domestic animal.

So perhaps the evolution of grandpuppy status is not such a far-fetched progression between man and his best friend.

"When we look at the evolution of the dog from protector, hunter, to companion, it may not be so unlikely for the dog to appear in the 'family tree,' " said Dr. Rebecca Johnson, director of the Research Center for Human-Animal Interaction at University of Missouri College of Veterinary Medicine.

Since women in today's society are waiting a bit later to have children, granddogs "may play a family role somewhat like a child," notes Johnson.

These furry creatures apparently offer some of the healthiest relationships in a family, too.

A grandpuppy is a canine member of the family that provides unconditional love...--Dr. Rebecca Johnson

"A grandpuppy is a canine member of the family that provides unconditional love, diversion, something to talk about, a reason to exercise (dog walking), a source of relaxation and stress relief," said Johnson.

Perhaps it's not surprising then that grandpuppy-parents will go to any measure to bond with their four-legged family members, even if it's a long-distance relationship. Take 86-year-old Dolores Corley and her husband, 85-year-old Ralph. They interact with their grandpuppy, Gracie, via Skype.

"Since we live in St. Louis and our grandpuppy lives in Atlanta, we find using Skype a great way to keep up with Gracie -- and of course our daughter Maureen, too," said Dolores.

"It's fun to see Gracie, a Boxer Terrier mix, on the computer screen since we rarely get to visit with her in person."

Grandpuppy retail products are very popular with consumers.

In addition to connecting with grandpuppies online, a connection with these canines has evolved in the retail market, as well. Clothing, dog bowls, note cards, mouse pads, coffee cups and coasters with "grandpuppy" images on them are among the items dog lovers can purchase for themselves and their pooches.

"It's a popular product, and we sell more than 1,000 grandpuppy designs on our website," said Mike Karns, marketing director of a company called zazzle.com.

Khris Klaich owns a pet gift store in Buffalo, New York, and he says customers ask him "all of the time" if he carries grandpuppy products.

Others are more skeptical of the shelf-life of these retail items.

"The proliferation of grandpuppy merchandise is a great example of an animal fad," Herzog said. "Some of these become part of the culture, and some just disappear," he noted.

"It's hard to say if people will be talking about their grandpuppies 10 years from now."

But for now, a growing segment of people are talking about their grandpuppies -- and with passionate conviction.